Fan-turbine rotor assembly for a tip turbine engine

ABSTRACT

A fan-turbine rotor assembly ( 24 ) for a tip turbine engine ( 10  )includes a fan hub ( 64 ) with an outer periphery ( 112 ) scalloped by a multitude of elongated openings ( 114 ) which extend into a fan hub web ( 115 ). Each elongated opening defines an inducer receipt section ( 117 ) to receive an inducer section ( 66 )and a hollow fan blade section ( 72 ). An inducer exhaust from each inducer section is located adjacent a core airflow passage ( 80 ) within each fan blade section to provide communication therebetween.

BACKGROUND OF THE INVENTION

The present invention relates to a tip turbine engine, and moreparticularly to a fan-turbine rotor assembly which provides mechanicalretention between a multitude of rotational components.

An aircraft gas turbine engine of the conventional turbofan typegenerally includes a forward bypass fan a compressor, a combustor, andan aft turbine all located along a common longitudinal axis. Acompressor and a turbine of the engine are interconnected by a shaft.The compressor is rotatably driven to compress air entering thecombustor to a relatively high pressure. This pressurized air is thenmixed with fuel in a combustor and ignited to form a high energy gasstream. The gas stream flows axially aft to rotatably drive the turbinewhich rotatably drives the compressor through the shaft. The gas streamis also responsible for rotating the bypass fan. In some instances,there are multiple shafts or spools. In such instances, there is aseparate turbine connected to a separate corresponding compressorthrough each shaft. In most instances, the lowest pressure turbine willdrive the bypass fan.

Although highly efficient, conventional turbofan engines operate in anaxial flow relationship. The axial flow relationship results in arelatively complicated elongated engine structure of considerablelongitudinal length relative to the engine diameter. This elongatedshape may complicate or prevent packaging of the engine into particularapplications.

A recent development in gas turbine engines is the tip turbine engine.Tip turbine engines locate an axial compressor forward of a bypass fanwhich includes hollow fan blades that receive airflow from the axialcompressor therethrough such that the hollow fan blades operate as acentrifugal compressor. Compressed core airflow from the hollow fanblades is mixed with fuel in an annular combustor and ignited to form ahigh energy gas stream which drives the turbine integrated onto the tipsof the hollow bypass fan blades for rotation therewith as generallydisclosed in U.S. Pat. application publication Nos.: 20030192303;20030192304; and 20040025490.

The tip turbine engine provides a thrust to weight ratio equivalent toconventional turbofan engines of the same class within a package ofsignificantly shorter length.

One significant rotational component of a tip turbine engine is thefan-turbine rotor assembly. The fan-turbine rotor assembly includesintricate components, which rotate at relatively high speeds to generatebypass airflow while communicating a core airflow through each of themultitude of hollow fan blades. A large percentage of the expenseassociated with a tip turbine engine is the manufacture of thefan-turbine rotor assembly.

Accordingly, it is desirable to provide an assembly arrangement for afan-turbine rotor assembly, which is relatively inexpensive tomanufacture yet provides a high degree of reliability.

SUMMARY OF THE INVENTION

The fan-turbine rotor assembly for a tip turbine engine according to thepresent invention includes a fan hub, which has an outer peripheryscalloped by a multitude of elongated openings, which extend into a fanhub web. Each elongated opening defines an inducer receipt section toreceive an inducer section and a blade receipt section to retain ahollow fan blade section. The blade receipt section retains each of thehollow fan blade sections adjacent each inducer section. An inner fanblade mount is located adjacent an inducer exhaust from each inducersection to engage the inducer hub with the fan hub and provide a coreairflow communication path from the inducer passages within each inducersection into the core airflow passage within each fan blade section.

The inducer sections and fan blade sections are directionally mountedwithin the fan hub such that the forces exerted upon the fan-turbinerotor assembly during operation further lock the inducer sections andfan blade sections into the fan hub. That is, operational forcesmaintain the fan-turbine rotor assembly in an assembled condition ratherthan operating to disassemble the components.

The present invention therefore provides an assembly arrangement for afan-turbine rotor assembly which is relatively inexpensive tomanufacture yet provides a high degree of reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1 is a partial sectional perspective view of a tip turbine engine;

FIG. 2 is a longitudinal sectional view of a tip turbine engine along anengine centerline;

FIG. 3 is an exploded view of a fan-turbine rotor assembly;

FIG. 4 is an assembled view of a fan-turbine rotor assembly;

FIG. 5 is an expanded perspective view of an inducer section;

FIG. 6 is an expanded perspective view of the fan-turbine rotorassembly;

FIG. 7 is an expanded perspective view of a partially assembledfan-turbine rotor assembly; and

FIG. 8 is a tear sectional view of the engagement between an inducerreceipt section, a blade receipt section, an inducer section and a fanblade section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a general perspective partial sectional view of a tipturbine engine type gas turbine engine 10. The engine 10 includes anouter nacelle 12, a nonrotatable static outer support structure 14 and anonrotatable static inner support structure 16. A multitude of fan inletguide vanes 18 are mounted between the static outer support structure 14and the static inner support structure 16. Each inlet guide vanepreferably includes a variable trailing edge 18A.

A nose cone 20 is preferably located along the engine centerline A tosmoothly direct airflow into an axial compressor 22 adjacent thereto.The axial compressor 22 is mounted about the engine centerline A behindthe nose cone 20.

A fan-turbine rotor assembly 24 is mounted for rotation about the enginecenterline A aft of the axial compressor 22. The fan-turbine rotorassembly 24 includes a multitude of hollow fan blades 28 to provideinternal, centrifugal compression of the compressed airflow from theaxial compressor 22 for distribution to an annular combustor 30 locatedwithin the nonrotatable static outer support structure 14.

A turbine 32 includes a multitude of tip turbine blades 34 (two stagesshown) which rotatably drive the hollow fan blades 28 relative to amultitude of tip turbine stators 36 which extend radially inwardly fromthe static outer support structure 14. The annular combustor 30 isaxially forward of the turbine 32 and communicates with the turbine 32.

Referring to FIG. 2, the nonrotatable static inner support structure 16includes a splitter 40, a static inner support housing 42 and an staticouter support housing 44 located coaxial to said engine centerline A.

The axial compressor 22 includes the axial compressor rotor 46 fromwhich a plurality of compressor blades 52 extend radially outwardly anda compressor case 50 fixedly mounted to the splitter 40. A plurality ofcompressor vanes 54 extend radially inwardly from the compressor case 50between stages of the compressor blades 52. The compressor blades 52 andcompressor vanes 54 are arranged circumferentially about the axialcompressor rotor 46 in stages (three stages of compressor blades 52 andcompressor vanes 54 are shown in this example). The axial compressorrotor 46 is mounted for rotation upon the static inner support housing42 through a forward bearing assembly 68 and an aft bearing assembly 62.

The fan-turbine rotor assembly 24 includes a fan hub 64 that supports amultitude of the hollow fan blades 28. Each fan blade 28 includes aninducer section 66, a hollow fan blade section 72 and a diffuser section74. The inducer section 66 receives airflow from the axial compressor 22generally parallel to the engine centerline A and turns the airflow froman axial airflow direction toward a radial airflow direction. Theairflow is radially communicated through a core airflow passage 80within the fan blade section 72 where the airflow is centrifugallycompressed. From the core airflow passage 80, the airflow is turned anddiffused toward an axial airflow direction toward the annular combustor30. Preferably the airflow is diffused axially forward in the engine 10,however, the airflow may alternatively be communicated in anotherdirection.

A gearbox assembly 90 aft of the fan-turbine rotor assembly 24 providesa speed increase between the fan-turbine rotor assembly 24 and the axialcompressor 22. Alternatively, the gearbox assembly 90 could provide aspeed decrease between the fan-turbine rotor assembly 24 and the axialcompressor rotor 46. The gearbox assembly 90 is mounted for rotationbetween the static inner support housing 42 and the static outer supporthousing 44. The gearbox assembly 90 includes a sun gear shaft 92 whichrotates with the axial compressor 22 and a planet carrier 94 whichrotates with the fan-turbine rotor assembly 24 to provide a speeddifferential therebetween. The gearbox assembly 90 is preferably aplanetary gearbox that provides co-rotating or counter-rotatingrotational engagement between the fan-turbine rotor assembly 24 and anaxial compressor rotor 46. The gearbox assembly 90 is mounted forrotation between the sun gear shaft 92 and the static outer supporthousing 44 through a forward bearing 96 and a rear bearing 98. Theforward bearing 96 and the rear bearing 98 are both tapered rollerbearings and both handle radial loads. The forward bearing 96 handlesthe aft axial loads while the rear bearing 98 handles the forward axialloads. The sun gear shaft 92 is rotationally engaged with the axialcompressor rotor 46 at a splined interconnection 100 or the like.

In operation, air enters the axial compressor 22, where it is compressedby the three stages of the compressor blades 52 and compressor vanes 54.The compressed air from the axial compressor 22 enters the inducersection 66 in a direction generally parallel to the engine centerline Aand is turned by the inducer section 66 radially outwardly through thecore airflow passage 80 of the hollow fan blades 28. The airflow isfurther compressed centrifugally in the core airflow passage 80 of thehollow fan blades 28 by rotation of the hollow fan blades 28. From thecore airflow passage 80, the airflow is turned and diffused axiallyforward in the engine 10 into the annular combustor 30. The compressedcore airflow. from the hollow fan blades 28 is mixed with fuel in theannular combustor 30 and ignited to form a high-energy gas stream. Thehigh-energy gas stream is expanded over the multitude of tip turbineblades 34 mounted about the outer periphery of the fan blades 28 todrive the fan-turbine rotor assembly 24, which in turn drives the axialcompressor 22 through the gearbox assembly 90. Concurrent therewith, thefan-turbine rotor assembly 24 discharges fan bypass air axially aft tomerge with the core airflow from the turbine 32 in an exhaust case 106.A multitude of exit guide vanes 108 are located between the static outersupport housing 44 and the nonrotatable static outer support structure14 to guide the combined airflow out of the engine 10 to provide forwardthrust. An exhaust mixer 110 mixes the airflow from the turbine blades34 with the bypass airflow through the fan blades 28.

Referring to FIG. 3, the fan-turbine rotor assembly 24 is illustrated inan exploded view. The fan hub 64 is the primary structural support ofthe fan-turbine rotor assembly 24 (FIG. 4). The fan hub 64 is preferablyforged and then milled to provide the desired geometry. The fan hub 64defines a bore 110 and an outer periphery 112. The outer periphery 112is preferably scalloped by a multitude of elongated openings 114 locatedabout the outer periphery 112. The elongated openings 114 extend into afan hub web 115.

Each elongated opening 114 defines an inducer receipt section 117 toreceive each inducer section 66. The inducer receipt section 117generally follows the shape of the inducer section 66. That is, theinducer receipt section 117 receives the more complicated shape of theinducer section 66 without the necessity of milling the more complicatedshape directly into the fan hub 64.

The inducer sections 66 are essentially conduits that define an inducerpassage 118 between an inducer inlet 120 and an inducer exit 128 (alsoillustrated in FIG. 5). Preferably, the inducer sections 66 are formedof a composite material.

The inducer sections 66 together form an inducer 116 of the fan-turbinerotor assembly 24. The inducer inlet 120 of each inducer passage 118extends forward of the fan hub 64 and is canted toward a rotationaldirection of the fan hub 64 such that inducer inlet 120 operates as anair scoop during rotation of the fan-turbine rotor assembly 24 (FIG. 6).Each inducer passage 118 provides separate airflow communication to eachcore airflow passage 80 when each fan blade section 72 is mounted withineach elongated opening 114.

Inducer sections 66 are preferably uni-directionally assembled into thefan hub 64 from the front such that the forces exerted upon thefan-turbine rotor assembly 24 during operation correspond with furtherlocking of the inducer sections 66 into the fan hub 64. Each inducerinlet 120 preferably at least partially overlaps the next inducer inlet120 when assembled into the fan hub 64 (FIG. 4) through the overlappedorientation the inducer inlets 120 lock the inducer sections 66 into thefan hub 64. That is, operational forces maintain the inducer sections 66within the fan hub 64 in an assembled condition rather than operating todisassemble the components. Alternatively, or in addition the inducersections 66 may be mounted to the fan hub 64 through an attachment suchas bonding, welding, rivets, threaded fasteners, and the like.

Referring to FIG. 6, the fan hub 64 retains each hollow fan bladesection 72 within each elongated opening 114 through a blade receiptsection 122. The blade receipt section 122 preferably forms an axialsemi-cylindrical opening 125 (also illustrated in FIG. 7) formed alongthe axial length of the elongated openings 114. It should be understoodthat other retention structures will likewise be usable with the presentinvention.

Referring to FIG. 7, each hollow fan blade section 72 includes an innerfan blade mount 124 that corresponds with the blade receipt section 122to retain the hollow fan blade section 72 within the fan hub 64. Theinner fan blade mount 124 preferably includes a semi-cylindrical portion127 to radially retain the fan blade 28 through a dove-tail, fir-tree,or bulb-type engagement structure (FIG. 8). The fan hub 64 supports thehoop load required to retain the integrity of the disk/blade structure.

The inner fan blade mount 124 is preferably uni-directionally mountedinto the blade receipt section 122 from the rear face of the fan hub 64.The inner fan blade mount 124 engages the blade receipt section 122during operation of the fan-turbine rotor assembly 24 to provide adirectional lock therebetween. That is, the inner fan blade mount 124and the blade receipt section 122 may be frustoconical or axiallynon-symmetrical such that the forward segments 124 a, 127 a form asmaller engagement surface than the rear segment 124 b, 127 b to providea wedged engagement therebetween when assembled.

Referring to FIG. 8, each inducer section 66 is further retained withinthe fan hub 64 by interaction with the inner fan blade mount 124. Thatis, the inner fan blade mount 124 engages the inducer exit 126 (FIG. 5)to further retain the inducer sections 66 into the fan hub 64 to providecore airflow communication through the inducer passages 118 and into thecore airflow passage 80. Seals 128 may be additionally located betweeneach inducer section 66 and each hollow fan blade section 72

It should be understood that relative positional terms such as“forward,”“aft,” “upper,” “lower,” “above,” “below,” and the like arewith reference to the normal operational attitude of the vehicle andshould not be considered otherwise limiting.

The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

1. A fan assembly for a tip turbine engine comprising: a fan hubdefining an axis of rotation, said fan hub defining a multitude ofelongated openings located about an outer periphery of said fan hub,each of said elongated openings extend to a fan hub web, define aninducer receipt section to receive an inducer section at least thereinand a blade receipt section to retain a hollow fan blade sectionadjacent each of said inducer sections, said blade receipt sectionincludes a dove tail engagement; and an inducer mountable at leastpartially within said multitude of elongated openings to provide adirectional lock therebetween, said inducer defining a multitude ofinducer passages which turn an airflow from an axial airflow directiongenerally along said fan axis of rotation to a radial airflow direction.2. The fan assembly as recited in claim 1, wherein said inducer includesa multitude of inducer sections each of which are independentlyreceivable within one of said multitude of elongated openings.
 3. Thefan assembly as recited in claim 1, wherein each of said inducersections defines an inducer passage inlet.
 4. The fan assembly asrecited in claim 3, wherein each of said inducer passage inletscommunicates with each of said inducer passages defined by each of saidinducer sections.
 5. The fan assembly as recited in claim 4, whereinsaid inducer passage inlets are canted toward a rotational direction ofsaid fan hub, each of said inducer sections at least partiallyoverlapping an adjacent inducer section.
 6. The fan assembly as recitedin claim 1, further comprising a fan blade section having a tip turbine,each of said fan blade sections mounted within each of said elongatedopenings, each of said fan blade sections defining a fan blade coreairflow passage to receive said airflow from a respective inducerpassages therethrough.
 7. A fan hub for a tip turbine engine comprising:a fan hub defining an axis of rotation, said fan hub defining amultitude of elongated openings located about an outer periphery of saidfan hub, each of said elongated openings extends to a fan hub web todefine an inducer receipt section to receive an inducer section at leasttherein and a blade receipt section to retain a hollow fan blade sectionadjacent each of said inducer sections, wherein each of said elongatedopenings extends through a front face and an aft face of said fan hub todefine a scalloped outer periphery.
 8. A fan hub for a tip turbineengine comprising: a fan hub defining an axis of rotation, said fan hubdefining a multitude of elongated openings located about an outerperiphery of said fan hub, each of said elongated openings extends to afan hub web to define an inducer receipt section to receive an inducersection at least therein and a blade receipt section to retain a hollowfan blade section adjacent each of said inducer sections wherein each ofsaid elongated openings is non-parallel to said axis of rotation.
 9. Amethod of assembling a fan assembly for a tip turbine engine comprisingthe steps of: mounting an inducer section within each of a multitude ofelongated openings formed in a fan hub from a front face of the fan hub,the fan hub defining an axis of rotation, the inducer defining amultitude of inducer passages which turn an airflow from an axialairflow direction generally along said fan axis of rotation to a radialairflow direction; mounting a fan blade section within each of themultitude of elongated openings, each of the fan blade sections locatedadjacent and radially outboard of each of the inducer sections, each ofsaid fan blade sections defining a fan blade core airflow passage toreceive said airflow from a respective inducer passage therethrough; andmounting a tip turbine about an outer periphery of each fan bladesection.
 10. A fan assembly for a tip turbine engine comprising: a fanhub defining an axis of rotation, said fan hub defining a multitude ofelongated openings located about an outer periphery of said fan hub,each of said elongated openings defines an axially non-symmetricalengagement surface to provide a wedged engagement between each of saidmultitude of elongated openings and a fan blade section; and an inducermountable at least partially within said multitude of elongated openingsfrom a front face of the fan hub, said inducer defining a multitude ofinducer passages which turn an airflow from an axial airflow directiongenerally along said fan axis of rotation to a radial airflow direction,each of said multitude of inducer passages defining an inducer passageinlet canted toward a rotational direction of said fan hub to engage anadjacent inducer passage inlet to provide a directional locktherebetween.